U.S. patent application number 11/150170 was filed with the patent office on 2006-12-14 for method of securing a shim to a brake pad assembly backing plate and brake pad assembly obtained thereby.
Invention is credited to Stewart Kahan, Patrick Savage, Kenneth Schouten.
Application Number | 20060278482 11/150170 |
Document ID | / |
Family ID | 37523131 |
Filed Date | 2006-12-14 |
United States Patent
Application |
20060278482 |
Kind Code |
A1 |
Kahan; Stewart ; et
al. |
December 14, 2006 |
Method of securing a shim to a brake pad assembly backing plate and
brake pad assembly obtained thereby
Abstract
The method of manufacturing a brake pad assembly for use in a
disc brake assembly, comprises the following steps: providing a
backing plate defining distinct shim and friction pad surfaces, the
backing plate destined to carry a friction pad on the friction pad
surface and comprising at least one recess on the backing plate
shim surface, the recess defining an inner peripheral wall having a
top rim; providing a shim defining an abutment surface; applying
the shim abutment surface against the backing plate shim surface;
and forcing the shim to deform locally into the recess and against
the recess inner peripheral wall so that a shim lip projecting
transversely away from the shim abutment surface will be forced to
deform towards the recess inner peripheral wall to become
pressure-fitted within the recess thereby securing the shim to the
backing plate.
Inventors: |
Kahan; Stewart;
(Dollard-des-Ormeaux, CA) ; Savage; Patrick;
(Cornwall, CA) ; Schouten; Kenneth; (Hudson,
CA) |
Correspondence
Address: |
LESPERANCE & MARTINEAU
1440 WEST
STE-CATHERINE ROOM 700
MONTREAL
QC
H3G1R8
CA
|
Family ID: |
37523131 |
Appl. No.: |
11/150170 |
Filed: |
June 13, 2005 |
Current U.S.
Class: |
188/250G ;
188/250R |
Current CPC
Class: |
F16D 65/092 20130101;
F16D 65/0006 20130101; F16D 2250/00 20130101; F16D 2250/0092
20130101 |
Class at
Publication: |
188/250.00G ;
188/250.00R |
International
Class: |
F16D 65/38 20060101
F16D065/38 |
Claims
1. A method in a brake pad assembly for use in a disc brake
assembly, of securing a shim to a backing plate, with said backing
plate defining distinct shim and friction pad surfaces and destined
to carry a friction pad on said friction pad surface, and with said
shim defining an abutment surface, said method comprising the
following steps: forming at least one recess in said backing plate
shim surface, said recess defining an inner peripheral wall having
a top rim; applying said shim abutment surface against said backing
plate shim surface; and forcing said shim to deform locally into
said recess and against said recess inner peripheral wall so that a
shim lip projecting transversely away from said shim abutment
surface will be forced to deform towards said recess inner
peripheral wall to become pressure-fitted within said recess
thereby securing said shim to said backing plate.
2. A method as defined in claim 1, comprising the following step
before the step of applying said shim abutment surface against said
backing plate shim surface: forming at least one embossment on said
shim, said embossment defining said shim lip about an embossment
hole and defining an embossment bottom wall within said embossment
hole integrally formed with said lip; wherein the step of applying
said shim abutment surface against said backing plate shim surface
is accomplished so that said shim embossment registers with said
backing plate recess and so that said shim lip extends into said
backing plate recess.
3. A method as defined in claim 1, comprising the following steps
before the step of applying said shim abutment surface against said
backing plate shim surface: forming at least one hole through said
shim; and forming said lip on said shim about said hole; wherein
the step of applying said shim abutment surface against said
backing plate shim surface is accomplished so that said shim hole
registers with said backing plate recess and so that said shim lip
extends into said backing plate recess.
4. A method as defined in claim 1, further comprising the following
step before said shim abutment surface is applied against said
backing plate shim surface: forming an annular shoulder on said
backing plate at said inner peripheral wall rim that projects
within said recess, wherein upon said shim lip being deformed
against said recess inner peripheral wall, said shim lip will
partly engage an area underneath said annular shoulder within said
recess to be axially retained by said annular shoulder.
5. A method as defined in claim 4, wherein said annular shoulder is
formed in said recess by said backing plate formed with said recess
being subjected to an abrasive grit blasting operation.
6. A method as defined in claim 3, wherein said hole is formed on
said shim by a punching operation accomplished before said shim
abutment surface is applied against said backing plate shim
surface, said lip being formed concurrently with said hole due to
the material of said shim plastically deforming during said
punching operation and bending outwardly transversely of said shim
abutment surface.
7. A method as defined in claim 2, wherein said shim lip is forced
to deform against said recess inner peripheral wall by means of a
coining punch that is driven into said hole and said recess when
said lip engages said recess, with the diameter of said coining
punch being larger than the diameter of said shim lip.
8. A method as defined in claim 3, wherein said shim lip is forced
to deform against said recess inner peripheral wall by means of a
coining punch that is driven into said hole and said recess when
said lip engages said recess, with the diameter of said punch being
larger than the diameter of said shim lip to deform said shim lip
against said recess inner peripheral wall in a pressure-fitted
fashion.
9. A method as defined in claim 8, wherein said coining punch is
power-driven into said hole and said recess against the bias of a
biasing member biasing said punch away from said hole and said
recess, and said punch is retrieved from said hole and said recess
by the action of said biasing member.
10. A method as defined in claim 8, further comprising the
following step before said shim abutment surface is applied against
said backing plate shim surface: forming an annular shoulder on
said backing plate at said inner peripheral wall rim that projects
within said recess, wherein upon said shim lip being deformed
against said recess inner peripheral wall, said shim lip will
partly engage an area underneath said annular shoulder within said
recess to be axially retained by said annular shoulder; wherein
upon said coining punch being driven into said hole and said
recess, not only will said shim lip deform against said recess
inner peripheral wall, but also said shim lip will force said
annular shoulder to elastically yieldingly stretch to allow the
insertion of said coining punch in said hole and said recess, with
said annular shoulder springing back towards its initial position
under its intrinsic resiliency upon said coining punch being
retrieved from said hole and said recess, said annular shoulder
thus gripping said shim lip.
11. A method as defined in claim 3, wherein there are three
recesses formed in said backing plate shim surface and three holes
bordered by corresponding lips formed in said shim.
12. A method of manufacturing a brake pad assembly for use in a
disc brake assembly, comprising the following steps: providing a
backing plate defining distinct shim and friction pad surfaces,
said backing plate destined to carry a friction pad on said
friction pad surface and comprising at least one recess on said
backing plate shim surface, said recess defining an inner
peripheral wall having a top rim; providing a shim defining an
abutment surface; applying said shim abutment surface against said
backing plate shim surface; and forcing said shim to deform locally
into said recess and against said recess inner peripheral wall so
that a shim lip projecting transversely away from said shim
abutment surface will be forced to deform towards said recess inner
peripheral wall to become pressure-fitted within said recess
thereby securing said shim to said backing plate.
13. A method as defined in claim 12, wherein in the step of
providing said shim, said shim comprises at least one embossment
comprising said lip about an embossment hole and an embossment
bottom wall integrally formed with said lip within said embossment
hole, with the step of applying said shim abutment surface against
said backing plate shim surface being accomplished so that said
shim embossment registers with said backing plate recess and so
that said shim lip extends into said backing plate recess.
14. A method as defined in claim 12, wherein in the step of
providing said shim, said shim comprises at least one hole and is
provided with said lip about said hole, with the step of applying
said shim abutment surface against said backing plate shim surface
being accomplished so that said shim hole registers with said
backing plate recess and so that said shim lip extends into said
backing plate recess.
15. A method as defined in claim 12, wherein said backing plate
comprises an annular shoulder at said inner peripheral wall rim
projecting within said recess, wherein upon said shim lip being
deformed against said recess inner peripheral wall, said shim lip
will partly engage an area underneath said annular shoulder within
said recess to be axially retained by said annular shoulder.
16. A method as defined in claim 14, wherein said shim lip is made
with material of said shim that plastically deformed when said hole
was formed and bending outwardly transversely of said shim abutment
surface.
17. A method as defined in claim 14, wherein said shim lip is
forced to deform against said recess inner wall by means of a punch
that is driven into said hole and said recess when said lip engages
said recess, with the diameter of said punch being larger than the
diameter of said shim lip.
18. A method as defined in claim 17, wherein said punch is
power-driven into said hole and said recess against the bias of a
biasing member biasing said punch away from said hole and said
recess, and said punch is retrieved from said hole and said recess
by the action of said biasing member.
19. A method as defined in claim 17, wherein in the step of
providing said backing plate, said backing plate comprises an
annular shoulder at said inner peripheral wall rim that projects
within said recess, wherein upon said shim lip being deformed
against said recess inner peripheral wall, said shim lip will
partly engage an area underneath said annular shoulder within said
recess to be axially retained by said annular shoulder; and wherein
upon said coining punch being driven into said hole and said
recess, not only will said shim lip deform against said recess
inner peripheral wall, but also said shim lip will force said
annular shoulder to elastically yieldingly stretch to allow the
insertion of said coining punch in said hole and said recess, with
said annular shoulder springing back towards its initial position
under its intrinsic resiliency upon said coining punch being
retrieved from said hole and said recess, said annular shoulder
thus gripping said shim lip.
20. A brake pad assembly for use in a disc brake assembly,
comprising: a backing plate defining distinct shim and friction pad
surfaces; a friction pad fixedly attached to said backing plate on
said friction pad surface; a recess made in said backing plate on
said shim surface, said recess defining an inner bottom wall and an
inner peripheral wall having a top rim; a shim defining an abutment
surface resting against said backing plate shim surface; a hole
made in said shim and registering with said recess; a lip
integrally carried by said shim and projecting within said recess
transversely away from said shim abutment surface about said hole,
said lip being formed peripherally about a same axis as said hole
and engaging said recess inner peripheral wall in pressure-fitted
fashion.
21. A brake pad assembly as defined in claim 20, wherein said
backing plate defines an annular shoulder projecting inwardly of
said recess at said recess inner peripheral wall top rim, with said
lip engaging an area within said recess underneath said shoulder
whereby said shim is retained by said shoulder.
22. A brake pad assembly as defined in claim 20, wherein said shim
defines an embossment defining said hole, with said shim further
defining an embossment bottom wall integrally formed with said lip
within said embossment hole.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to brake pad assemblies for
vehicle disc brake assemblies, and more particularly to a method of
securing a shim to a brake pad assembly backing plate.
BACKGROUND OF THE INVENTION
[0002] In a vehicle disc brake assembly, a disc rotor rotates with
the axle of the wheel to be braked. A generally U-shaped caliper
engages the disc, with the caliper carrying a pair of brake pad
assemblies positioned on opposite sides of the disc. Each brake pad
assembly comprises a steel backing plate equipped with a
corresponding molded friction pad fixedly attached to the backing
plate in facing register with the disc. As the backing plates move
inwardly under the force supplied by an actuator piston carried by
the caliper, the inner surfaces of the friction pads are engaged in
frictional braking contact with the disc. Vibration of the brake
members during braking actuation can produce an undesirable high
pitched brake squeal noise.
[0003] To reduce or eliminate the undesired brake squeal noise,
sound dampening members, commonly referred to as shims, have been
used by both original equipment manufacturers and by brake repair
shops. These noise dampening shims are substantially flat metallic
plates positioned between the actuated piston and the back surface
of the related brake pad assembly steel backing plate and also
between the caliper and the back surface of the related brake pad
assembly steel backing plate.
[0004] Unfortunately, this frictional contact can cause a torque or
twisting force on the shim by the related piston or caliper
producing a shearing force in the adhesive of the shim if adhesive
is employed to attach the shim to the backing plate. Under the
extreme conditions of heat and vibration that the brake pad
assemblies are subjected to, the adhesive by itself is not
sufficient to prevent accidental dislodging of the shim from the
backing plate during braking. Excessive vibration can cause any
mechanical fastener (such as a staple or rivet) to detach from the
assembly and become accidentally lodged between the caliper piston
and the brake pad, potentially affecting performance of the braking
system.
[0005] It is known to provide brake pad assemblies that are
designed to further reduce shifting of the shim during braking,
that include shims having one or more extruded holes that align
with corresponding preformed aligned recesses in the back surface
of the backing plate. Fasteners such as rivets are driven through
the shim holes and the backing plate recesses, to integrally anchor
the shim to the backing plate. However, not only are the rivets
subject to accidental dislodgement during use, as indicated
hereinabove, but also the production of the brake pad assembly is
complicated by the installation of these rivets. However, this
construction yields a very desirable reduction on the shearing
motion of the shim, in addition to the shim providing its known
noise dampening effect.
[0006] According to this latter brake pad assembly embodiment, the
brake pad assembly backing plates are prepared prior to the shims
being installed thereon. Firstly, the backing plates are washed
clean of any lubricants or rust preventatives that may have been
employed during the stamping process. The cleaned metal backing
plates are then subjected to an abrasive grit blasting operation in
which small metal pellets are blasted against the backing plate, to
increase the surface roughness thereof, for example in range of 300
to 500 micro inches. This is done for the purpose of
SUMMARY OF THE INVENTION
[0007] The present invention relates to a method in a brake pad
assembly for use in a disc brake assembly, of securing a shim to a
backing plate, with said backing plate defining distinct shim and
friction pad surfaces and destined to carry a friction pad on said
friction pad surface, and with said shim defining an abutment
surface, said method comprising the following steps:
[0008] forming at least one recess in said backing plate shim
surface, said recess defining an inner peripheral wall having a top
rim;
[0009] applying said shim abutment surface against said backing
plate shim surface; and
[0010] forcing said shim to deform locally into said recess and
against said recess inner peripheral wall so that a shim lip
projecting transversely away from said shim abutment surface will
be forced to deform towards said recess inner peripheral wall to
become pressure-fitted within said recess thereby securing said
shim to said backing plate.
[0011] In one embodiment, the method also comprises the following
step before the step of applying said shim abutment surface against
said backing plate shim surface:
[0012] forming at least one embossment on said shim, said
embossment defining said shim lip about an embossment hole and
defining an embossment bottom wall within said embossment hole
integrally formed with said lip;
wherein the step of applying said shim abutment surface against
said backing plate shim surface is accomplished so that said shim
embossment registers with said backing plate recess and so that
said shim lip extends into said backing plate recess.
[0013] In an alternate embodiment, the method instead comprises the
following steps before the step of applying said shim abutment
surface against said backing plate shim surface:
[0014] forming at least one hole through said shim; and
[0015] forming said lip on said shim about said hole;
wherein the step of applying said shim abutment surface against
said backing plate shim surface is accomplished so that said shim
hole registers with said backing plate recess and so that said shim
lip extends into said backing plate recess.
[0016] In one embodiment, the method further comprises the
following step before said shim abutment surface is applied against
said backing plate shim surface:
[0017] forming an annular shoulder on said backing plate at said
inner peripheral wall rim that projects within said recess, wherein
upon said shim lip being deformed against said recess inner
peripheral wall, said shim lip will partly engage an area
underneath said annular shoulder within said recess to be axially
retained by said annular shoulder.
[0018] In one embodiment, said annular shoulder is formed in said
recess by said backing plate formed with said recess being
subjected to an abrasive grit blasting operation.
[0019] In one embodiment, said hole is formed on said shim by a
punching operation accomplished before said shim abutment surface
is applied against said backing plate shim surface, said lip being
formed concurrently with said hole due to the material of said shim
plastically deforming during said punching operation and bending
outwardly transversely of said shim abutment surface.
[0020] In one embodiment, said shim lip is forced to deform against
said recess inner peripheral wall by means of a coining punch that
is driven into said hole and said recess when said lip engages said
recess, with the diameter of said coining punch being larger than
the diameter of said shim lip.
[0021] In one embodiment, said coining punch is power-driven into
said hole and said recess against the bias of a biasing member
biasing said punch away from said hole and said recess, and said
punch is retrieved from said hole and said recess by the action of
said biasing member.
[0022] In one embodiment, the method further comprises the
following step before said shim abutment surface is applied against
said backing plate shim surface:
[0023] forming an annular shoulder on said backing plate at said
inner peripheral wall rim that projects within said recess, wherein
upon said shim lip being deformed against said recess inner
peripheral wall, said shim lip will partly engage an area
underneath said annular shoulder within said recess to be axially
retained by said annular shoulder;
[0024] wherein upon said coining punch being driven into said hole
and said recess, not only will said shim lip deform against said
recess inner peripheral wall, but also said shim lip will force
said annular shoulder to elastically yieldingly stretch to allow
the insertion of said coining punch in said hole and said recess,
with said annular shoulder springing back towards its initial
position under its intrinsic resiliency upon said coining punch
being retrieved from said hole and said recess, said annular
shoulder thus gripping said shim lip.
[0025] In one embodiment, there are three recesses formed in said
backing plate shim surface and three holes bordered by
corresponding lips formed in said shim.
[0026] The present invention also relates to a method of
manufacturing a brake pad assembly for use in a disc brake
assembly, comprising the following steps:
[0027] providing a backing plate defining distinct shim and
friction pad surfaces, said backing plate destined to carry a
friction pad on said friction pad surface and comprising at least
one recess on said backing plate shim surface, said recess defining
an inner peripheral wall having a top rim;
[0028] providing a shim defining an abutment surface;
[0029] applying said shim abutment surface against said backing
plate shim surface; and
[0030] forcing said shim to deform locally into said recess and
against said recess inner peripheral wall so that a shim lip
projecting transversely away from said shim abutment surface will
be forced to deform towards said recess inner peripheral wall to
become pressure-fitted within said recess thereby securing said
shim to said backing plate.
[0031] In one embodiment, in the step of providing said shim, said
shim comprises at least one embossment comprising said lip about an
embossment hole and an embossment bottom wall integrally formed
with said lip within said embossment hole, with the step of
applying said shim abutment surface against said backing plate shim
surface being accomplished so that said shim embossment registers
with said backing plate recess and so that said shim lip extends
into said backing plate recess.
[0032] In an alternate embodiment, in the step of providing said
shim, said shim comprises at least one hole and is provided with
said lip about said hole, with the step of applying said shim
abutment surface against said backing plate shim surface being
accomplished so that said shim hole registers with said backing
plate recess and so that said shim lip extends into said backing
plate recess.
[0033] In one embodiment, said backing plate comprises an annular
shoulder at said inner peripheral wall rim projecting within said
recess, wherein upon said shim lip being deformed against said
recess inner peripheral wall, said shim lip will partly engage an
area underneath said annular shoulder within said recess to be
axially retained by said annular shoulder.
[0034] In one embodiment, said shim lip is made with material of
said shim that plastically deformed when said hole was formed and
bending outwardly transversely of said shim abutment surface.
[0035] In one embodiment, said shim lip is forced to deform against
said recess inner wall by means of a punch that is driven into said
hole and said recess when said lip engages said recess, with the
diameter of said punch being larger than the diameter of said shim
lip.
[0036] In one embodiment, said punch is power-driven into said hole
and said recess against the bias of a biasing member biasing said
punch away from said hole and said recess, and said punch is
retrieved from said hole and said recess by the action of said
biasing member.
[0037] In one embodiment, in the step of providing said backing
plate, said backing plate comprises an annular shoulder at said
inner peripheral wall rim that projects within said recess, wherein
upon said shim lip being deformed against said recess inner
peripheral wall, said shim lip will partly engage an area
underneath said annular shoulder within said recess to be axially
retained by said annular shoulder;
[0038] and wherein upon said coining punch being driven into said
hole and said recess, not only will said shim lip deform against
said recess inner peripheral wall, but also said shim lip will
force said annular shoulder to elastically yieldingly stretch to
allow the insertion of said coining punch in said hole and said
recess, with said annular shoulder springing back towards its
initial position under its intrinsic resiliency upon said coining
punch being retrieved from said hole and said recess, said annular
shoulder thus gripping said shim lip.
[0039] The present invention further relates to a brake pad
assembly for use in a disc brake assembly, comprising:
[0040] a backing plate defining distinct shim and friction pad
surfaces;
[0041] a friction pad fixedly attached to said backing plate on
said friction pad surface;
[0042] a recess made in said backing plate on said shim surface,
said recess defining an inner bottom wall and an inner peripheral
wall having a top rim;
[0043] a shim defining an abutment surface resting against said
backing plate shim surface;
[0044] a hole made in said shim and registering with said
recess;
[0045] a lip integrally carried by said shim and projecting within
said recess transversely away from said shim abutment surface about
said hole, said lip being formed peripherally about a same axis as
said hole and engaging said recess inner peripheral wall in
pressure-fitted fashion.
[0046] In one embodiment, said backing plate defines an annular
shoulder projecting inwardly of said recess at said recess inner
peripheral wall top rim, with said lip engaging an area within said
recess underneath said shoulder whereby said shim is retained by
said shoulder.
[0047] In one embodiment, said shim defines an embossment defining
said hole, with said shim further defining an embossment bottom
wall integrally formed with said lip within said embossment
hole.
DESCRIPTION OF THE DRAWINGS
[0048] In the annexed drawings:
[0049] FIG. 1 is a perspective view of a brake pad assembly
according to the present invention;
[0050] FIG. 2 is an exploded perspective view of the brake pad of
FIG. 1;
[0051] FIG. 3 is an enlarged diametrical cross-sectional view of a
recess of the backing plate of the brake pad of FIG. 1, with the
recess being shown in its initial configuration before the abrasive
grit blasting operation;
[0052] FIG. 4 is similar to FIG. 3, but showing the recess in its
final configuration after the abrasive grit blasting operation,
with the inwardly projecting shoulder formed at the top rim of the
recess being emphasized to facilitate the visual appreciation of
same; and
[0053] FIGS. 5, 6 and 7 sequentially show a punch being inserted
into and then retrieved from the mutually registering shim hole and
backing plate recess of the brake pad assembly to secure the shim
to the backing plate.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0054] FIGS. 1 and 2 show a brake pad assembly 20 for use in a disc
brake assembly (not shown) for motor vehicles. Brake pad assembly
20 comprises a substantially flat backing plate 22 defining a shim
surface 24 and a friction pad surface 26 opposite shim surface 24.
A friction pad 28 is fixedly attached to backing plate 22 on
friction pad surface 26.
[0055] At least one recess, and for example three recesses 30a,
30b, 30c (generally referred to as recesses 30 in the present
specification), are made in backing plate 22 on its shim surface
24. As shown in FIG. 3, each recess 30 defines an inner bottom wall
32 and an inner peripheral wall 34 having a top rim 36.
[0056] A noise dampening shim 38 is installed on backing plate 22
in a manner described hereinafter. Shim 38 defines a substantially
flat abutment surface 40 and an opposite free surface 42, with
abutment surface 40 resting against backing plate shim surface 24.
Free surface 42 will be located between backing plate 22 and either
the caliper (not shown) or the caliper piston (not shown) once
brake pad assembly 20 is operatively installed in a disc brake
assembly (not shown). Shim 38 comprises at least one hole, and for
example three holes 44a, 44b, 44c (generally referred to as holes
44 in the present specification).
[0057] According to the present invention, there is provided a
method in the brake pad assembly 20 of securing shim 38 to backing
plate 22. First, backing plate 22, which can be made of any
suitable material such as SAEI010-1018 hot rolled or cold rolled
steel (optionally covered by a known protective coating), is
stamped according to known stamping methods and embossed to form
recesses 30 on its shim surface 24. Recesses 30 can be made with
any suitable depth or diameter that allow the present invention to
be carried out--as will be obvious for someone skilled in the art
of the present invention--for example with a depth of 0.055 inch to
0.065 inch and a diameter of 0.195 inch to 0.205 inch and with a
20.degree. draft (see FIG. 3). Backing plate 22 is then washed
clean of any lubricants or rust preventatives that may have been
employed in the stamping process. The clean metal backing plates
are thereafter subjected to an abrasive grit blasting operation in
which small metal pellets are blasted against the backing plate to
increase the surface roughness to a suitable degree, for example in
the range of 300 to 500 micro inches (average value). The purpose
of this operation in prior art methods was to provide optimum
surface contact area for an adhesion promoter substance of known
composition that is added to the backing plate 22 prior to
compression molding the friction pad 28 to the backing plate
22.
[0058] However, unexpected and advantageous results have been found
when a backing plate 22 is subjected to the abrasive grit blasting
operation where recesses 30 are pre-made therein. Indeed, in such a
case the configuration of the inner cavity of recesses 30 is
changed by the high-velocity pellet flow therein, whereby instead
of keeping the generally inwardly convex shape provided by the
inwardly convergent peripheral wall 34 configuration shown in FIG.
3, the final shape of recesses 30 is as shown in FIG. 4, i.e.
recess 30 then comprises a slightly inwardly concave shape and
defines an annular shoulder 46 that projects radially inwardly at
the recess inner peripheral wall top rim 36. FIG. 3 and FIGS. 4-7
respectively show backing plate 22 before and after the abrasive
grit blasting operation, with the inwardly concave shape of recess
30 and with the inward bulge of shoulder 46 being exaggerated in
FIGS. 4-7 to more clearly show the effect of the grit blasting
operation.
[0059] Shim 38 can be made of any suitable material, preferably a
ferrous or non-ferrous metal. Each hole 44 is pierced through shim
38 with a suitable piercing punch (not shown), with the piercing
punch not only forming holes 44 but in the process plastically
deforming the metallic shim to form a lip 48 carried by shim 38 and
projecting transversely away from shim abutment surface 40 about
hole 44. Lip 48 is thus formed peripherally about a same axis as
its corresponding hole 44.
[0060] To secure shim 38 to the prepared backing plate 22, shim 38
is applied against backing plate 22, and more particularly the shim
abutment surface 40 is applied against the backing plate shim
surface 24 so that the shim hole 44 registers with the backing
plate recesses 30 and so that the shim lips 48 project into the
backing plate recesses 30, as shown in FIG. 5.
[0061] Then, a coining punch 50 is used to secure shim 38 to
backing plate 22. Coining punch 50 comprises a sleeve 52 in which a
piston 54 is axially movable. Piston 54 has a striking head 56 of a
desired dimension, which will be larger than the inner diameter of
lip 48 of shim hole 44. Thus, upon coining punch head 56 being
inserted into hole 44 as shown in FIG. 6, the latter will be
widened and shim lip 48 will be forced to deform against the recess
inner peripheral wall 34 so that the shim lip 48 will become
pressure-fitted within recess 30 thereby securing shim 38 to
backing plate 22.
[0062] More particularly, according to the embodiment shown in the
annexed drawings, lip 48 will deform and partly engage the area
underneath shoulder 46 of the recess peripheral wall rim 36.
Although the simple pressure-fit of lip 48 against a straight
recess peripheral wall 34 might be sufficient to retain shim 38 to
backing plate 22, this engagement of lip 48 under shoulder 46 will
significantly help prevent accidental disengagement of shim 38 from
backing plate 22.
[0063] After coining punch head 56 is power-driven into hole 44 and
recess 30, it is retrieved therefrom by the action of a biasing
member in the form of a spring 58 that abuts against the free
surface 42 of shim 38 (as suggested in FIG. 6) and that biases
punch head 56 away from hole 44 and recess 30 when punch head 56 is
inserted therein. Thus, punch head 56 may be retrieved from hole 44
and recess 30 as suggested in FIG. 7.
[0064] To promote a positive pressure-fit of lip 48 against the
hole peripheral wall 34, not only is the diameter of coining punch
head 56 larger than that of lip 48 and hole 44, but also the
diameter of punch head 56 is such that even the backing plate
shoulder 46 will slightly yieldingly move outwardly under the bias
of lip 48 being stretched by punch head 56, upon punch head 56
being inserted into recess 30. This outward diametrical increase of
shoulder 46 is temporary however, i.e. this is not a plastic
deformation but rather an elastic deformation. Indeed, upon punch
head 56 being retrieved from recess 30, shoulder 46 will inwardly
spring back towards its initial position under its intrinsic
resiliency, thus firmly gripping lip 48 to increase the
pressure-fit of lip 48 in recess 30 and consequently to further
secure shim 38 to backing plate 22.
[0065] It is understood that if there are more than one hole 44 and
recess 30 in which a coining punch is to be driven, one punch per
hole 44 and recess 30 may be used to allow a single punching
operation in which all punches are simultaneously driven into
corresponding holes 44 and recesses 30 to accelerate the entire
process.
[0066] Also, it is noted that although the method of manufacturing
the brake pad assembly described hereinabove includes the step of
piercing a hole through shim 38 before shim 38 is applied against
backing plate 22, alternate ways to carry out the invention are
envisioned wherein the shim is simply embossed instead of being
pierced, in which case the embossment will also define an inner lip
similar to the one shown in the annexed drawings in addition to an
embossment bottom wall integrally formed with the lip; or wherein
the shim is neither embossed nor pierced prior to being applied
against the backing plate shim surface, with the shim instead being
forced upon the coining punch being driven into the backing plate
recess to deform locally into the backing plate recess and against
the recess inner peripheral wall so that a shim lip will
concurrently become pressure-fitted within the recess peripheral
wall thereby securing said shim to said backing plate. Thus, it can
be seen that the shim lip can be formed either when a shim hole or
embossment is being formed prior to the shim being applied against
the backing plate, or alternately when the coining punch is used to
secure the shim to the backing plate after the shim is applied to
the backing plate. In all embodiments, the shim is deformed locally
within the recess when the coining punch is driven into the shim
hole, and a shim lip is formed at one point or another to become
pressure-fitted within a corresponding backing plate recess.
[0067] It is further noted that a single pair of mutually
registering recess 30 and hole 44 could be sufficient to retain
shim 38 to backing plate 22.
[0068] Recesses 30 may be formed according to any suitable process,
including milling, punching, stamping, drilling, or any other
manner in which recesses 30 may be formed. Likewise, hole 44 may be
formed according to any suitable process. It is understood however
that by punching a hole 44 through shim 38, a lip 48 is
concurrently formed, which is advantageous since it does not
require an additional step in the manufacturing process of shim 38.
However, other means of forming a lip could also be envisioned,
including adding a lip after hole 44 has been pierced.
[0069] It is noted that the step of applying the shim abutment
surface against the backing plate shim surface will be accomplished
so that the shim holes register with the corresponding backing
plate recesses and so that the shim lips extend into the backing
plate recesses only if the holes are preformed in the shim.
However, in the case where no holes or embossments are preformed in
the shim, applying the shim against the backing plate is
accomplished by simply resting the shim against the backing plate;
in such a case, other alignment means could be used if necessary to
properly position the shim.
[0070] In view of the above comments, the method of the present
invention can be defined as follows:
[0071] forming at least one recess in the backing plate shim
surface, the recess defining an inner peripheral wall having a top
rim;
[0072] applying the shim abutment surface against the backing plate
shim surface; and
[0073] forcing the shim to deform locally into the recess and
against the recess inner peripheral wall so that a shim lip will
become pressure-fitted within the recess thereby securing the shim
to the backing plate.
[0074] Also, the method of the present invention can be defined as
follows:
[0075] providing a backing plate defining distinct shim and
friction pad surfaces, the backing plate destined to carry a
friction pad on the friction pad surface and comprising at least
one recess on the backing plate shim surface, the recess defining
an inner peripheral wall having a top rim;
[0076] providing a shim defining an abutment surface;
[0077] applying the shim abutment surface against the backing plate
shim surface; and
[0078] forcing the shim to deform locally into the recess and
against the recess inner peripheral wall so that a shim lip will
become pressure-fitted within the recess against the recess inner
peripheral wall, whereby the shim becomes secured to the backing
plate.
[0079] Any further modification to the above-described embodiments
which would be obvious to a person skilled in the art of the
present invention, is considered to be encompassed within the scope
of the appended claims.
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